Acoustic properties of vowels in clear and conversational speech by female non-native English speakers

Abstract

Studies have shown that talkers can improve the intelligibility of their speech when instructed to speak as if talking to a hearing-impaired person. The improvement of speech intelligibility is associated with specific acoustic-phonetic changes: increases in vowel duration and fundamental frequency (F0), a wider pitch range, and a shift in formant frequencies for F1 and F2. Most previous studies of clear speech production have been conducted with native speakers; research with second language speakers is much less common. The present study examined the acoustic properties of non-native English vowels produced in a clear speaking style. Five female Cantonese speakers and a comparison group of English speakers were recorded producing four vowels (/i u ae a/) in /bVt/ context in conversational and clear speech. Vowel durations, F0, pitch range, and the first two formants for each of the four vowels were measured. Analyses revealed that for both groups of speakers, vowel durations, F0, pitch range, and F1 spoken clearly were greater than those produced conversationally. However, F2 was higher in conversational speech than in clear speech. The findings suggest that female non-native English speakers exhibit acoustic-phonetic patterns similar to those of native speakers when asked to produce English vowels clearly.